Intro -- Introduction and Motivation -- CHAPTER 1 Experimental methods -- 1.1 Heteroepitaxial growth of AlN on sapphire -- 1.2 AlN templates as UV LED base layers -- 1.3 State of research -- CHAPTER 2 Experimental methods -- 2.1 Sample fabrication -- 2.2 Characterisation methods -- 2.3 Method for light extraction simulations -- CHAPTER 3 High temperature annealing of MOVPE grown AlN -- 3.1 Annealing of 350 nm thick AlN -- 3.2 Annealing of layer thickness series -- 3.3 Variation of the annealing parameters -- CHAPTER 4 Nanopatterned sapphire substrates -- 4.1 Light extraction simulations of nanopatternedinterface -- 4.2 Growth on sapphire nanopillars -- 4.3 Growth on sapphire nanoholes -- CHAPTER 5 UVC LED performance on the developed AlN templates -- Conclusion -- APPENDIX A
